Advanced aerospace vehicles and engines require resilient seals capable of blocking high temperature flow. Pressure and thermal loads can cause movements between adjoining elements that can be both in-plane and out-of-plane. Thermal distortions can be caused by temperature gradients and differences in coefficients of thermal expansion (CTE) between adjoining elements. These movements can change the size of gaps between components that the seals are required to seal. These conditions require seals that can withstand and block high temperature gases while tracking the movements of adjacent structural components. Additionally, the seals must be flexible and capable of sealing around corners and curved structures.
Conventional braided rope seals composed of ceramics and superalloys provide adequate flow-blocking characteristics for advanced gas turbine applications up to 2000 F. However, these seal designs exhibit significant permanent set and hysteresis when subjected to repeated load cycles at high temperatures. Thermal barriers being considered for space vehicle re-entry control surface seals may exhibit considerable permanent set after 1900 F temperature exposure. The seals may fail to return to their original shape and diametral height after load cycling.